Prostanoids such as prostaglandin (PG), thromboxane (TX) and leukotriene (LT) are the family of oxidized metabolites of arachidonic acid, and demonstrate various physiological actions for maintaining local homeostasis in the living body (The Pharmacological Basis of Therapeutics (Gilman, A. G., Goodman, L. S., Rall, T. W., and Murad, F., eds) 7th Ed., pp 660, Macmillan Publishing Co., New York (1985)). Their physiological actions are regulated through a membrane-bound receptor specific for each prostanoid (Annu. Rev. Pharm. Tox., 10, 213 (1989) Prostanoids and their Receptors. In Comprehensive Medicinal Chemistry., pp 643 (1990), Pergamon Press, Oxford). Prostaglandin E (PGE), a member of prostanoids, especially prostaglandin E2 (PGE2) participates widely in contraction and relaxation of gastrointestinal tract, secretion of gastric acid, relaxation of smooth muscle, and release of neurotransmitters. Based on the results obtained by the analysis of physiological and pharmacological actions of PGE2 and its site of action, it is thought that there are 4 subtype receptors including EP1, EP2, EP3 and EP4 (Negishi M. et al, J. Lipid Mediators Cell Signalling, 12, 379-391 (1995)) and that each receptor is involved in a different signal transduction.
Among them, it is known that EP1 is involved in pain, fever and diuresis (Br. J. Pharmacol., 1994, 112, 735-40, European J. Pharmacol., 152 (1988) 273-279, Gen Pharmacol., September 1992, 23(5) p805-809). Therefore, it is thought that antagonizing the receptor may be effective for treating pain, fever and pollakiuria. To clarify these points, it is essential to analyze a structure of EP1 receptor, a signaling and tissue distribution of the receptor.
The amino acid sequence of EP1 receptor (Accession No. AAC37539.1) and the nucleotide sequence encoding it (Accession No. L22647) are disclosed in Japanese Patent No. 3,090,472. However, detailed comparison of the sequences with those of human EP1 receptor of the present invention revealed that there are 4 discrepancies in nucleotide sequence and 2 in amino acid sequence, respectively.
The amino acid sequence of the polypeptide of the present invention was searched against the SwissProt amino acid sequence databases (Swiss Prot Release2.0), there was no identical sequence that corresponded to the polypeptide. The nucleotide sequence of the DNA encoding the polypeptide of the present invention was also searched against the GenBank nucleotide sequence databases (GenBank Release70.0), no identical sequence that corresponded to the DNA was found. Accordingly, it was confirmed that the polypeptide of the present invention was a novel one.